When digging work is carried out using this digging bit, a bit body is recovered by being pulled out from a borehole after the borehole is formed to reach a predetermined depth. However, if the borehole is formed in rocks which are likely to collapse, a wall in the borehole may collapse, and a rear end side of the bit body may be covered with debris. Consequently, in some cases, the bit body cannot be removed from the borehole. Therefore, as disclosed in PTL 1 for example, a retractable bit in which a cutting blade is disposed in a rear end portion of the bit body is used in this case.